A weak-coupling superconductivity in the electron doped NaFe${}_{0.95}$Co${}_{0.05}$As is revealed by ARPES

We report a systematic study on the electronic structure and superconducting (SC) gaps in electron doped NaFe${}_{0.95}$Co${}_{0.05}$As superconductor using angle-resolved photoemission spectroscopy. Hole-like Fermi sheets are at the zone center and electron-like Fermi sheets are at the zone corner, and are mainly contributed by $xz$ and $yz$ orbital characters. Our results reveal a $\frac{\mathrm{\Delta }}{K_B{T}_c}$ in the range of 1.8-2.1, suggesting a weak-coupling superconductivity in these compounds. Gap closing above the transition temperature ($T_c$) shows the absence of pseudogaps. Gap evolution with temperature follow the BCS gap equation near the $\mathrm{\Gamma }$, $Z$, and $M$ high symmetry points. Furthermore, an almost isotropic superconductivity along $k_z$ direction in the momentum space is observed by varying the excitation energies.